1. Field of the Invention
The present invention relates generally to smoke generators and more particularly to eletrically-heated smoke generators particularly suited for air flow studies.
2. Description of the Prior Art
It is desirable in many circumstances to generate smoke for use in air flow studies, sky writing, and similar circumstances. A particular area of research in which smoke generators are important is in the study of vortices created by the wakes of modern aircraft, particularly the very large multiple engine craft now in use for transporting cargo and personnel.
In making such studies, it is desirable that devices be made available for generating smoke on a continuous basis and that such devices are preferably relatively small and reliable in structure to permit mounting at the wing tips of aircraft or within wind tunnels and similar environments.
In the past, smoke bombs have been used for air flow studies, but have proven to be unsatisfactory in view of their capability of producing smoke for only a relatively short interval. Relatively large and complex smoke generators have also been designed which provided an adequate smoke supply of long-term duration, but which required the burning of a fuel, such as gasoline, for the production of smoke. A specific example of a device of this type is disclosed in U.S. Pat. No. 3,242,098 to Andrews. The Andrews device is large and complex, creating additional hazards when used in the environment mentioned above.
Other types of portable smoke or fog generating devices are known, such as those described in U.S. Pat. No. 3,496,668 to Slater et al. and in U.S. Pat. No. 3,675,360 to Pierce. However, devices of the type described in these patents are not suitable for use with aircraft or in wind tunnels, and generally produce a large particle, toxic mist not suitable for use in air flow studies.
A variety of smoke generators are also known which produce smoke particles of a desirable type through electric heating of appropriate smoke generating materials. Examples of such devices are disclosed in U.S. Pat. Nos. 2,324,359 to Callan, 3,160,980 to Seuthe and 3,432,439 to Dickman. However, all of these devices are complicated, expensive to produce and lack the high level of reliability and efficiency desirable in smoke generators to be used on aircraft or in wind tunnels.
A need therefore exists for an improved smoke generator particularly suitable for use in air flow studies